Resumen de Ecophysiological factor effect on growth rate, lag phase and ochratoxin A production by Aspergillus niger aggregate strains on irradiated peanut seeds
Andrea Astoreca, Carla Barberis, Carina Elizabeth Magnoli, Mariana Combina, Ana Maria Dalcero
The aims of this study were to evaluate the effects of water activity, temperature, incubation time and their interactions on lag phase, growth rate and ochratoxin A (OTA) production by strains belonging to the Aspergillus niger aggregate on irradiated peanut seeds. In the temperature and water activity range assayed, the optimal conditions of growth for RCP42 and RCP176 strains on irradiated peanut seeds were 0.995 aw and 30 °C being the growth rates of 12.4 and 14.6 mm/day, respectively. The maximum OTA production occurred at 0.973 aw and 25 °C for both strains assayed; whereas the minimum OTA production was obtained at 0.951 aw and 15 °C, at 14 and 21 days of incubation for RCP42 and RCP176 strains, respectively. The amount of OTA accumulated during 21 days assayed by both strains varied from 6.5 to 460 μg/g and from 10 to 210 μg/g with mean levels of 119.2 and 97.5 μg/g for RCP42 and RCP176 strains, respectively. The variance analysis (ANOVA) revealed that OTA concentration produced by RCP42 strain was significantly (p < 0.0001) greater than that produced by RCP176 strain. If the strains with which the experiments were carried out were representative of the Aspergillus niger aggregate toxigenic species and the water activity in peanut seeds stored at 0.910 or lower was maintained, OTA production would be reduced during at least 21 days at variable temperatures.
